Conventionally, in the process of abrasion in combination with electrolytic polishing in which an electrolytic operation is combined with abrasion performed by an abrasive matter, when a band-shape material is continuously conveyed and polished for many hours, abrasive matters wear out and the need for exchanging the abrasive matters arises. However, working efficiency is greatly reduced if the conveyance of a band-shape material is interrupted for the exchange of the abrasive matters.